1. Field of the Invention
The present invention is related to a pneumatic control valve, and in particular to such an apparatus having a pneumatic motor operator, a translationally movable valve stem between motor operator and valve, and a position controller having an output means which can be interchanged without deteriorating the function of the motor operator.
2. Description of the Prior Art
German Patent 37 27 008 discloses a pneumatic control valve apparatus having a pneumatic motor operator, a translationally movable valve stem between the motor operator and a valve, a position controller having an output means which can be interchanged without deteriorating the function of the motor, a transmission means for transmitting the position of the valve stem onto a movable transmission rod of the position controller, and a yoke that rigidly connects the motor operator and a valve housing to one another. The transmission rod of the position controller and the transmission means are arranged in a space of the housing closed on all sides.
German Patent 37 27 008 is an improvement on the basic arrangement disclosed by German Published Application 31 16 640. In German Patent 32 27 008, the parts of the arrangement that image and transmit the valve position onto the position controller are protected against access from the outside and thus against influencing and/or damage without losing their easy replaceability.
The arrangements disclosed in German Published Application 37 27 008 and German Patent 31 16 640 provide position controllers having a rotational action. Consequently, the transmission rod of the position controller in these arrangements is a rotational lever. Consequently, the transmission means acts as an articulation means that transmits the translational movement of the valve stem onto the rotational lever as a rotary motion.
However, in an arrangement in which position controllers having a translational input are employed, there is a need to protect the parts that image and transmit the valve position onto the position controller against access from the outside, and thus against influencing and/or damage without losing their easy replaceability.